1. Field of the Invention
This invention relates to a magnetic disk cartridge. More particularly, this invention relates to a magnetic disk cartridge comprising a very thin, small-diameter disk-like recording medium used for recording and reproducing an image through high-speed rotation.
2. Description of the Prior Art
Recording media formed by coating a magnetic material on both surfaces of a disk-like flexible polyester sheet, i.e. floppy disks, were developed for recording therein digital information by use of a magnetic head. Since floppy disks are easy to handle and their cost is low, they are widely used as recording media for computers.
On the other hand, in still cameras, it has been proposed to take advantage of the usefulness of the floppy disks as described above and the merit thereof over silver halide emulsion films that the recording media can be reused for magnetic recording. Namely, it has been proposed to use a magnetic disk cartridge (hereinafter simply referred to as "cartridge") formed by decreasing the size of the floppy disk, i.e. decreasing the diameter and the thickness of the disk-like recording medium, and also reducing the size of the case for containing the recording medium so as to constitute a recording medium for recording and reproducing an image through high-speed rotation, Thus, there was developed a magnetic recording type still camera having approximately the same size as the conventional 35 mm camera.
The aforesaid cartridge is of the single-faced recording type wherein the video signals for one image are recorded in one track of the recording medium, and video signals for a larger number of images than can be recorded on a conventional standardized silver halide emulsion film, for example video signals for about 50 images, are recorded on one surface of the recording medium.
As described in Japanese Unexamined Utility Model Publication No. 57(1982)-110788, in the single-faced recording cartridge, it is necessary that a pair of magnetic head receiving holes formed in face-to-face relation in the bottom and top walls of the case be positioned near a diagonal line of the case so that the position of the magnetic head receiving holes may not be the same when the case is placed upside down, thereby to prevent the magnetic head for image recording and reproducing from contacting and damaging the recording medium when the cartridge is erroneously inserted upside down into an apparatus.
Further, since the cartridge is carried and used outdoors, it sometimes happens that the recording medium is affected by dust or contacted with and damaged by other materials. Therefore, when the magnetic head receiving holes are provided near a diagonal line of the case, it is necessary to close the magnetic head receiving holes in order to prevent dust from entering the case and protect the recording medium so that the magnetic layer of the recording medium will not be damaged due to contact with other materials.